Magazines carrying several rounds of ammunition have been used for many years to increase the fire power of a particular weapon. Some magazines are built into the weapon itself while others comprise a detachable accessory. Several magazines are made of plastic while others, especially those used by the military, are fabricated from metal. Both types use one or more springs attached to a follower to push the shells one-at-a-time up into position to be picked up by the bolt and shoved into the breech end of the barrel.
By far the majority of these magazines use some type of helical compression spring to advance the follower. Such springs have serious drawbacks in that the coils must stack atop one another thus taking up space in the bottom of the magazine that could otherwise be used to advantage for additional shells. They also need the bottom wall of the magazine as a fixed abutment to push against as they raise the follower and the shells stacked thereabove. Removing the bottom wall to clean or otherwise service the magazine, therefore, becomes somewhat of a problem in that the springs press against it constantly and they along with the follower come out once the wall has been removed. Reassembly is difficult for the same reasons.
An ideal solution would seem to lie in the use of so-called "negator" constant force springs which coil spirally instead of helically. By fastening one end of such a spring to the top of the magazine and letting the coil sit underneath the follower raising it upward as it recoils, several of the problems inherent in the use of helical springs for this purpose are overcome. To begin with, when the follower is at the bottom of the magazine and it is full of shells, the spring or springs are uncoiled so they take up very little space in the bottom thus enabling the magazine to carry additional shells. Moreover, since the springs are anchored at the top of the magazine and are, therefore, functionally independent of the bottom wall, the latter can easily be removed for cleanout while leaving the spring/follower subassembly intact.
If negator springs are so superior to helical ones for this application, the question naturally arises as to why the helical type is used at all. The answer, unfortunately, is that there is insufficient space alongside the stack of shells to accommodate negator springs when the magazine is designed for insertion into the handle of the weapon as opposed to one located underneath the receiver which is not particularly limited insofar as thickness is concerned. A helical spring positioned underneath the stack of shells, on the other hand, does not have to fit between the shell stack and magazine sidewall.
A further and even more difficult problem arises because the negator springs are not flat when unrolled but instead are inherently curved in such a way that even if there is enough space between the magazine sidewall and shell stack to receive one or more of them, their sharp side margins will dig into the shell casings and cause the magazine to jamb.
By way of further background, a special application of multi-round magazines of the type housed in the handle of the weapon has to do with the sport of rapid pistol fire, particularly as it relates to 0.45 caliber weapons. The rules require that the shooter place as many shots as possible "on target" during a predetermined timed interval. It is important, therefore, that the shooter be able to get off as many shots as he or she can before having to change magazines and also to make the change very quickly. Experts at this sport are able to eject the empty magazine and insert a new one before the empty one falls to the ground.